Early detection of cancer is key to improving prognosis and treatment outcomes. While blood tests alone cannot diagnose cancer, they provide valuable information about how the body is functioning and can alert to possible abnormalities that require further investigation.

This guide explains which types of blood tests are related to cancer, what tumor markers are, and how these results are interpreted in today’s medical context.

What Is a Blood Test and Why Can It Help Detect Diseases?

A blood test is one of the simplest and most useful tools in modern medicine. It analyzes different components of the bloodstream (such as red and white blood cells, platelets, proteins, enzymes, minerals, and hormones) to evaluate general health and detect potential imbalances in the body.

Blood reflects what happens in the body’s organs and systems. Therefore, a properly analyzed sample can provide early clues about metabolic, infectious, autoimmune, and even oncological diseases.

Today, clinical laboratories use advanced technology capable of detecting minimal variations in normal values, allowing early identification of organ or tissue changes before visible symptoms appear.

Moreover, blood testing is not only useful for early detection but also for monitoring treatments, assessing the function of vital organs like the liver and kidneys, and controlling the effects of medications.

For these reasons, performing regular blood tests at a trusted laboratory is an essential preventive health practice.

With platforms like Saludyvos, requesting an at-home blood test has never been easier. Through this tool, you can find the studies you need with transparent pricing, while the platform manages the home service so you can do it from the comfort of your home. The entire process complies with strict quality standards, ensuring reliable results without having to travel.

This way, you avoid unnecessary trips, save time, and keep your medical checkups up to date in a practical, comfortable, and safe way.

What Are Tumor Markers?

Tumor markers are biomolecules (such as proteins, antigens, or enzymes) found in the blood, urine, or body tissues. They are produced either by tumor cells or, in some cases, by the body itself in response to cancer.

Their presence or elevation can be associated with specific types of cancer, though this does not necessarily mean that a tumor is present. Marker levels may rise for benign reasons such as inflammation, infection, or other non-cancerous diseases.

Therefore, tumor markers cannot diagnose cancer by themselves; they are supportive tools within a broader approach that includes medical history, imaging studies, and, when necessary, a biopsy.

Tumor marker testing is particularly useful to:

• Guide diagnosis, helping physicians identify which organs or tissues to examine further.
• Evaluate treatment response, as a decrease in marker levels may indicate therapy effectiveness.
• Detects recurrence or disease progression, allowing ongoing monitoring after treatment.

Each tumor type tends to express specific markers, for example:

• PSA (Prostate-Specific Antigen) — linked to prostate cancer.
• CA 125 — used in ovarian cancer monitoring.
• CEA (Carcinoembryonic Antigen) — may rise in colon, pancreatic, ovarian, breast, thyroid medullary, lung, liver, stomach, or rectal cancers.

Common Blood Tests Related to Cancer

Complete Blood Count (CBC)

The CBC is one of the most frequently requested blood tests. It evaluates red and white blood cells and platelets, providing a general view of hematologic health.

While it does not detect cancer directly, it can show suggestive changes such as:

• Marked increase or decrease in white blood cells (possible leukemia or lymphoma).
  
• Persistent anemia (may suggest gastrointestinal or gynecologic cancers).
  
• Low platelet count (possible bone marrow involvement).
  

Checking normal CBC values and repeating the test periodically helps identify changes that may need follow-up.

PSA (Prostate-Specific Antigen)

PSA is a protein produced by prostate gland cells, and its measurement in blood is one of the most useful tests for assessing prostate health. Elevated PSA levels may be due to inflammation, infection, benign prostatic hyperplasia, or in some cases cancer.

PSA testing is mainly recommended for men over 50, or from age 45 if there is a family history of prostate cancer. Factors like age, heredity, and race (higher risk among Black men) influence cancer risk.

It can also be indicated if symptoms such as difficulty urinating, blood in urine or semen, pelvic pain, or incontinence appear.

For men already diagnosed with prostate cancer, PSA measurement is key for monitoring disease progression, assessing treatment response, and detecting recurrences early.

CA 125 (Cancer Antigen 125)

CA 125 is a protein found on the surface of certain body cells, especially in ovarian, uterine, and abdominal tissues. Elevated CA 125 levels can occur in ovarian cancer but also in benign conditions like endometriosis, menstruation, pelvic inflammatory disease, or benign ovarian cysts.

For patients with ovarian cancer, CA 125 testing is particularly useful for monitoring treatment, detecting recurrences, and assessing disease progression.

CEA (Carcinoembryonic Antigen)

CEA is a glycoprotein usually present at very low or undetectable levels in healthy adults. Its concentration can rise in certain cancers (colon, pancreas, lung, breast, ovary, liver, stomach, thyroid, or rectum) and in non-cancerous conditions such as smoking, liver disease, or inflammatory bowel disease.

Because of its limited specificity, CEA testing is mainly used for monitoring, not initial diagnosis. For example, in colorectal cancer, regular CEA measurement helps track treatment effectiveness and detect early recurrences.

AFP (Alpha-fetoprotein)

AFP is a protein normally produced by the fetal liver, so its levels in healthy adults are very low. Elevated AFP may indicate liver cancer, or certain ovarian or testicular tumors.

It can also rise in non-cancerous liver diseases such as chronic hepatitis or cirrhosis, which must be ruled out through imaging or additional tests. AFP measurement is useful for evaluating therapy response and detecting recurrences.

CA 19-9 (Cancer Antigen 19-9)

CA 19-9 is mainly elevated in pancreatic or bile duct cancers, but it may also rise in gastric, bladder, ovarian, colorectal, or liver cancers.

While it is not suitable as a screening test (since it can increase due to benign conditions like gallstones or pancreatitis), it is very helpful for monitoring pancreatic cancer progression and treatment response.

Other Useful Tests

Besides tumor markers, other blood tests can provide valuable insight into general health and cancer-related risks.

• Vitamin D: Low vitamin D levels have been linked to a higher risk of several chronic diseases, including some cancers. This nutrient helps regulate the immune system and supports cell growth and differentiation, so maintaining adequate levels contributes to better overall health and cancer prevention.
• Viral tests: Screening for infections such as Hepatitis C or mononucleosis may also be relevant in certain contexts. Chronic viral infections like Hepatitis B or C increase the risk of liver cancer, while others can mimic or overlap with malignant diseases. Including these in preventive checkups helps identify underlying causes and guide further evaluation.

Interpretation of Results: Always with Medical Guidance

It’s important to remember that no single abnormal blood test result confirms cancer. Results must always be interpreted by a medical professional, who will assess the clinical context, personal history, and factors that could influence the findings.

If your results are out of range, don’t panic—consult your doctor. They may recommend further testing (specific labs, imaging, or biopsy) to confirm or rule out a diagnosis.

Each lab marker is part of a bigger clinical picture, and proper interpretation is what allows accurate diagnosis and the best follow-up plan.

Conclusion

Blood tests are a fundamental tool for monitoring health and detecting serious diseases early, including cancer.

While tumor markers alone cannot confirm a diagnosis, their measurement helps guide medical evaluation, assess treatment response, and detect potential recurrences.

Getting regular checkups at a trusted laboratory, maintaining consistent medical follow-up, and adopting healthy lifestyle habits are essential pillars for protecting your health and acting in time.

With modern options like Saludyvos, it’s now possible to access reliable at-home blood testing services with the same quality as traditional labs—saving time, avoiding travel, and focusing on what truly matters: your health.